A centrifugal separator of this kind may be used to remove from a liquid body having a free liquid surface a thin surface layer of the liquid body and thereafter directly separate from each other two liquids with different density, e.g. oil and water, included in the surface layer.
A previously known centrifugal rotor having a pumping member of the initially defined kind is shown and described in WO 00/59639 and WO 00/59640.
In WO 00/59639 a centrifugal rotor of the kind here in question is proposed to be used together with a special device for removal of a surface layer from a liquid body. The pumping member of the centrifugal rotor in this case is arranged to pump liquid into the rotor from the special device and, thus, not to pump liquid into the rotor directly from the liquid body. A special device of this kind makes the entire separation equipment complicated and expensive.
In WO 00/59640 a centrifugal rotor having a pumping member of the initially defined kind, instead, is proposed to be provided with a special sealing device adapted to prevent liquid being pumped up from the liquid body from flowing on the outside of the pumping member and being thrown back therefrom to the liquid body. This would cause turbulence in the surface layer of the liquid body to be removed therefrom and to be treated in the centrifugal rotor. Thus, also in this case a special device is required in addition to the actual pumping member, i.e. the sealing device, for the pumping of liquid into the centrifugal rotor.
Centrifugal rotors having pumping members, intended to operate substantially as those in WO 00/59639 and WO 00/59640 but having no special devices for removal of a surface layer from a liquid body and no special sealing devices, respectively, are shown and described in U.S. Pat. No. 3,424,375, GB 884 812 and CH 345 599.
A main object of the present invention is to provide a centrifugal separator having a simple and inexpensive centrifugal rotor of the initially defined kind. Another object is to provide such a centrifugal separator which can effectively remove a surface layer from a liquid body and pump ft into the centrifugal rotor without causing substantial turbulence in the surface layer while this is still on the liquid body.